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SUNY Downstate Researchers Identify Areas of Plague Risk in Western U.S.

Findings May Be Used by Public Health Agencies to Aid in Plague Surveillance

Brooklyn, NY – Researchers at SUNY Downstate Medical Center have identified and mapped areas of high
probability of plague bacteria in the western United States. Their findings were published
in a recent edition of the journal, PeerJ.

This investigation predicted animal plague occurrence across western states based
on reported occurrences of plague in sylvan (wild) and domestic animal hosts. Plague
is a disease caused by Yersinia pestis, a bacterium found in rodents and their fleas
in many areas around the world.

“This study used surveillance data of plague in wild and domestic animals in the American
West to identify and map those areas with the greatest potential for human exposure
to this infection, which can be particularly deadly when transmitted to humans,” said
Michael Walsh, PhD, MPH, assistant professor in the Department of Epidemiology and
Biostatistics in the School of Public Health at SUNY Downstate.

"The findings can be used by public health agencies to target specific areas for enhanced
plague surveillance within areas and counties predicted to be at high risk, as well
as by other research teams to direct the sampling of local wildlife populations for
the identification of Yersinia pestis in wild animals that find themselves in close
proximity to humans and human developed landscapes," he added.

The citation for the article is:

Walsh M, Haseeb M. (2015) Modeling the ecologic niche of plague in sylvan and domestic
animal hosts to delineate sources of human exposure in the western United States.
PeerJ 3:e1493 https://doi.org/10.7717/peerj.1493.

According to the federal Centers for Disease Control and Prevention (CDC), plague
was first introduced into the United States in 1900, by rat–infested steamships that
had sailed from affected areas. Epidemics occurred in port cities, with the last urban
plague epidemic in the United States occurring in Los Angeles from 1924 through 1925.
Plague then spread from urban rats to rural rodent species, and became entrenched
in many areas of the western United States. Since that time, plague has occurred as
scattered cases in rural areas. Most human cases in the United States occur in two
regions: Northern New Mexico, northern Arizona, and southern Colorado; and California,
southern Oregon, and far western Nevada

The CDC also notes that in recent decades, an average of seven human plague cases
has been reported each year (range: 1–17 cases per year). Plague has occurred in people
of all ages (infants up to age 96), though 50% of cases occur in people ages 12–45.

The authors note in their article that while zoonotic (animal) transmission to humans
is much less common in modern times, significant plague risk remains in parts of the
western U.S. Moreover, risk to some threatened species that are part of the epizootic
cycle can be quite substantive.

This investigation attempted to predict the risk of plague across the western US by
modeling the ecologic niche of plague in sylvan and domestic animals identified between
2000 and 2015. An algorithm was used to predict this niche based on climate, altitude,
land cover, and the presence of an important enzootic (carrier) species, Peromyscus
maniculatus (a rodent commonly known as the North American deermouse).

This model demonstrated good predictive ability and identified areas of high risk
in central Colorado, north-central New Mexico, and southwestern and northeastern California.

The presence of P. maniculatus, altitude, precipitation during the driest and wettest quarters, and distance to
artificial surfaces, all contributed substantively to maximizing the gain function.
These findings add to the known landscape epidemiology and infection ecology of plague
in the western U.S. and may suggest locations of particular risk to be targeted for
wild and domestic animal intervention.

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About SUNY Downstate Medical Center

SUNY Downstate Medical Center, founded in 1860, was the first medical school in the
United States to bring teaching out of the lecture hall and to the patient’s bedside.
A center of innovation and excellence in research and clinical service delivery, SUNY
Downstate Medical Center comprises a College of Medicine, College of Nursing, School
of Health Professions, a School of Graduate Studies, School of Public Health, University
Hospital of Brooklyn, and a multifaceted biotechnology initiative including the Downstate
Biotechnology Incubator and BioBAT for early-stage and more mature companies, respectively.

SUNY Downstate ranks twelfth nationally in the number of alumni who are on the faculty
of American medical schools. More physicians practicing in New York City have graduated
from SUNY Downstate than from any other medical school.